In these years, a liquid crystal display device has rapidly become widely used instead of a cathode ray tube (CRT). Such a liquid crystal display device is widely applied to devices such as a liquid crystal television, a monitor, and a mobile phone, taking advantage of its features such as an energy-saving property, slimness, and lightness in weight. These features could be further effectively utilized by, for example, improving a backlight unit (light source unit), which is an illuminating device to be provided behind a liquid crystal display component.
The light source unit can be mainly classified into a side-light type light source unit and a direct type light source unit.
According to the side-light type light source unit, a light guide plate is provided behind a liquid crystal display component, and a light source is provided on a lateral edge of the light guide plate. The light source emits light and the light is reflected in the light guide plate so as to indirectly illuminate the liquid crystal display component evenly. This configuration makes it possible to (i) reduce a thickness of the backlight and (ii) realize an illuminating device achieving excellent luminance uniformity (although the luminance is low). Therefore, such a side-light type illuminating device has been mainly applied to a small/medium sized liquid crystal display device such as a mobile phone or a laptop computer.
On the other hand, according to the direct type light source unit, a plurality of light sources are provided behind a liquid crystal display component so that the plurality of light sources illuminate the liquid crystal display component directly. This configuration allows a large screen to achieve a high luminance. Accordingly, such a direct type light source unit has been mainly applied to a large liquid crystal display device having a screen size of 20 inches or more.
(Patent Literature 1)
For example, Patent Literature 1 discloses a configuration of the direct type light source unit.
Patent Literature 1 discloses an illuminating unit (light source unit) having a substantially rectangular housing in which a plurality of straight tubular light sources are arranged in parallel with a long side of the housing.